The 7 types of triangles: classification according to sides and angles

During our childhood, we all had to take math lessons in school, where we had to study the different types of triangles. However, over the years we may forget some things that we have studied. For some people math is a fascinating world, but others enjoy it more with the world of letters.

In this article we will go over the different types of trianglesIt may therefore be useful to brush up on some concepts studied in the past or to learn new things that were not known.

    Usefulness of triangles

    In mathematics, geometry is studied and different geometric figures such as triangles are studied in depth. This knowledge is useful for many reasons; for example: carrying out technical drawings or planning a structure and its construction.

    In this sense, and unlike a rectangle which can be turned into a parallelogram when force is applied to one of its sides, the sides of a triangle are fixed. Due to the rigidity of its shapes, physicists have shown that the triangle can withstand high forces without deforming. Therefore, architects and engineers use triangles when building bridges, roofs of houses and other structures. When triangles are embedded in structures, it increases resistance to reduced lateral movement.

    What is a triangle

    The triangle is a polygon, a flat geometric figure that has an area but no volume. all triangles have three sides, three vertices and three internal angles, the sum of which is 180 º

    The triangle consists of:

    • Mountain peak: Each of the points determined by a triangle and generally indicated by Latin capital letters A, B, C.
    • Based: It can be any of its sides, opposite the top.
    • size: It is the distance from one side to its opposite vertex.
    • sides: There are three of them and because of that they usually categorize triangles in different ways.

    In these figures, one side of this figure is always less than the sum of the other two sides, and in a triangle with equal sides, the opposite angles are also equal.

    How to calculate the perimeter and area of ​​a triangle

    Two measurements that we are interested in knowing about triangles are perimeter and area. To calculate the first, you have to add the lengths of all its sides:

    P = a + b + c

    Instead, to find out what the area of ​​this figure is, the following formula is used:

    A = ½ (bh)

    Therefore, the area of ​​the triangle is the base (b) by the height (h) divided by two, and the value resulting from this equation is expressed in square units.

    How triangles are classified

    There are different types of triangles and they are classified taking into account their length of their sides and the amplitude of their angles. Considering their sides, there are three types: equilateral, isosceles and scalene. Depending on their angles, we can distinguish right triangles, obtuse angles, acute angles and equiangles.

    Here we get to the details.

    Triangles according to the length of their sides

    Considering the length of the sides, the triangles can be of different types.

    1. Equilateral triangle

    An equilateral triangle has three sides of equal length, so it is a regular polygon. The angles of an equilateral triangle are also equal (60 ° each). The area of ​​this type of triangle is the root of 3 by 4 by the length of the square in the square. The perimeter is the product of the length of one side (l) by three (P = 3 l)

    2. Scale triangle

    A scalene triangle has three sides of different lengths, And their angles also have different sizes. The perimeter is equal to the sum of the lengths of its three sides. Let: P = a + b + c.

    3. Isosceles triangle

    An isosceles triangle has two equal sides and two equal angles, And the way to calculate its perimeter is: P = 2 l + b.

    Triangles according to angles

    Triangles can also be classified according to the magnitude of their angles.

    4. Triangular rectangle

    They are characterized by an internal right angle, with a value of 90 °. The legs are the sides that make up this angle, while the hypotenuse is the opposite side. The area of ​​this triangle is the product of its legs divided in half. Let: A = ½ (bc).

    5. Obtusangle triangle

    This type of triangle has an angle greater than 90 ° but less than 180 º which is said to be “obtuse”, And two acute angles less than 90 °.

    6. Acutangle triangle

    This type of triangle is characterized because it has its three angles less than 90 °

    7. Triangle triangle

    It is the equilateral triangle, since its internal angles are equal to 60 °.


    Almost all of them studied geometry in school and are familiar with triangles.. But over the years, many people can forget what their characteristics are and how they are classified. As you can see in this article, triangles are categorized in different ways based on the length of their sides and the width of their angles.

    Geometry is a subject studied in mathematics, but not all children enjoy this subject. In fact, some have serious difficulties. What are the causes? In our article “Children’s Difficulties Learning Mathematics”, we tell you.

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